slideshow86 Posted February 27, 2008 Share Posted February 27, 2008 Ok I have been searching for awhile now with not too much luck. Its soo hard to narrow the search down so I am forced to make a new thread. I have an 85 brat w/ a weber carb. I have no information on how this thing ran before I got it. I have replaced both fuel filters along w/ rebuilding the carb. Here goes. When I replaced the front fuel filter it filled back up to 3/4 full of fuel. Tried to get it running right to no avail. Went and got/replaced the rear filter. Noticed the front fuel filter is now empty (due to cranking all the fuel out of it) The fuel pump stopped pumping. I traced it to the plug and found a broken butt connector. I replaced the plug to the fuel pump but im getting very very low pressure. Once the level drops from half way on the front fuel filter, it becomes just a trickle. I no longer hear the pump working, but never really noticed it before either? Im wondering what the procedure is for testing a fuel pump and/or fpcu. At what times is the fuel pump powered. Does is have 2sec of power at key on then the rest durring cranking/running? Or is it ran off the tach signal? Thanks in advance. Jess Quote Link to comment Share on other sites More sharing options...
LPGsuperchargedBrumby Posted February 27, 2008 Share Posted February 27, 2008 it has no power until you crank it and power then stays on until about 0.5 sec after you kill the ignition. Quote Link to comment Share on other sites More sharing options...
Skip Posted February 27, 2008 Share Posted February 27, 2008 Jess, if you want to understand this system take a few minutes and read this post. http://www.ultimatesubaru.org/forum/showthread.php?t=82917 GD's post #10 tells a lot about this device. Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 27, 2008 Author Share Posted February 27, 2008 Thanks Skip. I have read a lot of posts about fuel issues, most of which are for mpfi or ea82. Having a hard time to find posts regarding my same MY. I don't know if my original setup is an internal vr or external. I know the new one I got is internal VR. I have been using the new alternator since the beginning and the accelerator pump was puttng out fuel so I didn't even look into it. I will try to find out which style I require and will inspect it with the old one. Is there a visual difference between the two? I have 12v on both sides of the coil. The choke is getting keyed power. The front filter used to be 3/4 full and when I noticed the ground wire from the fuel pump had came out of the back of the plug and re-hooked it back up. The pump seemed to pump very weak. If I am not getting full 12v at the pump, when running, it would be the circuit(short)/fpcu(unit, pickup in dizzy or tach signal)/ground( add ground to common ground). If I am getting full 12v threw (fuel pump) plug and the pump is pumping weak (both filters replaced), it would be the pump. I should be more clear, whats the best way to test the fpcu? I ran out of daylight and will test it all out afterwork. Thanks Jess Quote Link to comment Share on other sites More sharing options...
Skip Posted February 27, 2008 Share Posted February 27, 2008 "I should be more clear, whats the best way to test the fpcu?" I would run a pair of wires directly to the pump Pump side of the connector you speak of. Then connect a voltmeter to these wires. Watch the voltmeter when cranking with a fully charged bat. How did you or?? plumb the fuel return line to the Weber? Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 27, 2008 Author Share Posted February 27, 2008 "I should be more clear, whats the best way to test the fpcu?" I would run a pair of wires directly to the pump Pump side of the connector you speak of. Then connect a voltmeter to these wires. Watch the voltmeter when cranking with a fully charged bat. How did you or?? plumb the fuel return line to the Weber? Once I jump the fuel pump. do I test voltage of the wires I just jumped (wires that go to the pump) or the wires going to the fpcu? I was told I didn't need to run the return line? I don't know i f I have the right adaptor to hook it up to my weber. Would this cause low pressure? or negative vacuum on the pump? Also, when replacing the rear fuel filter, I thought someone said somewhere there were 3 hoses going into the rear fuel filter? (maybe not?) The rear filter was aftermarket and only had one input and one output. Don't know if this makes a difference. Thanks Quote Link to comment Share on other sites More sharing options...
Skip Posted February 27, 2008 Share Posted February 27, 2008 Once I jump the fuel pump. do I test voltage of the wires I just jumped (wires that go to the pump) or the wires going to the fpcu? The wires I speak of are only going tothe voltmeter - no jumping. I thought you could put the voltmeter somewhere you could see it while cranking. If I'm not mistaken?? You were asking how to check the voltage from the FPCU. I was told I didn't need to run the return line? I don't know i f I have the right adaptor to hook it up to my weber. Would this cause low pressure? or negative vacuum on the pump? No but it might explain this half full filter aspect you mention. Also, when replacing the rear fuel filter, I thought someone said somewhere there were 3 hoses going into the rear fuel filter? (maybe not?) The rear filter was aftermarket and only had one input and one output. Don't know if this makes a difference. Thanks The front filter (vapor separator) has three lines. Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 27, 2008 Author Share Posted February 27, 2008 The wires I speak of are only going tothe voltmeter - no jumping. Ok that makes a little more sence. ill make up a lead for it before I leave work. No but it might explain this half full filter aspect you mention. I had the return line disconnected from the very beginning and it was only after I replaced the rear filter and rehooked up the fuel pump, that I was getting the half full fuel filter thing. Anyone have any issues with not running the return line? The front filter (vapor separator) has three lines. Ok, my confusion. I just put in a regular filter and capped the return line. Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 28, 2008 Author Share Posted February 28, 2008 Ok so I tested the voltage at the pump. It is getting 13+ volts when cranking. Which leads me to believe that its either the pump or not having the return line is doing somthing weird? Ill need a fuel pressure guage to know for sure if fuel delivery is my issue then I can narrow it down more. Ive heard its only 1.5-3 lbs of pressure in the lines. That really isnt very many GPM is it? Is is supposed to fill the upper fuel filter up to 3/4? Or is 1/4 full ok ( I know this is a very bad analogy, but I dont have a fuel pressure guage yet and just wondering how full one's fuel filter is that has correct fuel pressure) ? I guess if I were to get it running under very lean conditions. High idle could be achieved and driving (and putting it under any sort of load) it up to half or 3/4 throttle could acount for the bucking and unhappy sounds, eh? I still need to figure out the choke. But all my issues could be around this faulty pump not delivering correct amount of fuel. When my car gets up to temp the flapper door things on the carb want to open all the way up. It wants to die at that point and I have to un-hook it just to make them close enough to run (wish I knew more about carbs ). I was thinking that once warm the choke is alowing more air and my lack of fuel is leaning it out too much to not let it run? I dont want to hurt anything if im warming this thing up to temp, at a really "lean" mixture. I did the test on my dizzy's vac advance and I think its shot. I found one new for $75 and am picking it up this weekend. I sure hope my car was origionally supposed to have a nippo-denso dizzy? (But at a warm state, I should be able to get the rmp's low enough that the vac advance wouldnt operate and I would be able to shoot time right?) But this probably wont fix all my issues. Oh the fun of my $100 brat turned $500(ish) brat already. Thanks for the extended help Skip Quote Link to comment Share on other sites More sharing options...
bratman2 Posted February 28, 2008 Share Posted February 28, 2008 I would think you would want the return line. May not have anything to do with your problem but when I converted my 87 brat to a Webber installing a regulator set for 2lbs. fuel pressure, sure helped things. The float does not have a lot of power to overide higher fuel pressure, also doesn't take a whole lot of fuel pressure to run a Webber. Maybe you should disconnect the hose at the filter at the pump, add a longer piece of hose and see what kind of flow you get into a jar. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 28, 2008 Share Posted February 28, 2008 Ok so I tested the voltage at the pump. It is getting 13+ volts when cranking. Sounds good. Which leads me to believe that its either the pump or not having the return line is doing somthing weird? I've run plenty of stock (carb) pumps without return lines. Both with Weber's and with stock carbs. Never has it been an issue. I've also never had a carb fuel pump fail. They really just don't die unless they get crap in them from a failed/no filter, or they starve for fuel and overheat. Ill need a fuel pressure guage to know for sure if fuel delivery is my issue then I can narrow it down more. Ive heard its only 1.5-3 lbs of pressure in the lines. That really isnt very many GPM is it? Is is supposed to fill the upper fuel filter up to 3/4? Or is 1/4 full ok ( I know this is a very bad analogy, but I dont have a fuel pressure guage yet and just wondering how full one's fuel filter is that has correct fuel pressure) ? I guess if I were to get it running under very lean conditions. High idle could be achieved and driving (and putting it under any sort of load) it up to half or 3/4 throttle could acount for the bucking and unhappy sounds, eh? The pump's are like 1.5 to 2.5 psi. "filling" of the filter tells you nothing. That's just trapped air that can't get out of the system. In order to fill the filter with fuel the air would have to go somewhere - but it can't once the float needle closes. The pump doesn't have enough pressure to displace the air even with a return line. Without the return it can't pump any volume at all. Pay no attention to the air. You are getting fuel - that's all that matters. I really doubt your problems are fuel pump related. Everything you have told me so far sounds normal to a trained ear. I still need to figure out the choke. But all my issues could be around this faulty pump not delivering correct amount of fuel. When my car gets up to temp the flapper door things on the carb want to open all the way up. It wants to die at that point and I have to un-hook it just to make them close enough to run (wish I knew more about carbs ). I was thinking that once warm the choke is alowing more air and my lack of fuel is leaning it out too much to not let it run? I dont want to hurt anything if im warming this thing up to temp, at a really "lean" mixture. Lean will not hurt it at idle unless you have severe misfiring. WOT is a different animal. Your problem is the idle circuit on the carb (talking fuel flow here, not electricity). Once the choke plates (those flappers you speak of ARE the choke) open, there is less vacuum on the idle circuit, and the mixture changes from very rich, to progressivly leaner. This allows the engine extra fuel durring warm up - fuel is easily condensed to a liquid on the cold cylinder walls of the engine so extra fuel is needed to make sure the final mixture is correct for the engine to idle. Something about your idle circuit is wrong - either it's plugged up, it's jetted wrong, or the mixture screw is way off. When tuning a Weber you NEVER tune cold. You don't even start tuning it till the engine reaches operating temp and the choke is fully pulled off. Then you start by setting the throttle cable posistion, and then the idle speed and mixure - they are a balancing act. The throttle plates should be fully closed and you should only have to adjust the mixture screw. If you have to change the speed screw (IE - lift the throttle plate off it's closed posistion) then you need to go up a size in idle jet. I did the test on my dizzy's vac advance and I think its shot. I found one new for $75 and am picking it up this weekend. I sure hope my car was origionally supposed to have a nippo-denso dizzy? Sadly, 4WD's all have Hitachi distributors, and 2WD's have the ND. Unless they have been swapped, which is possible but probably not likely. At any rate that's a total rip-off. You can have the vac-advance pot rebuilt for half that or less. Lookup Philbin Group. They have done a few for me and are very good at what they do. (But at a warm state, I should be able to get the rmp's low enough that the vac advance wouldnt operate and I would be able to shoot time right?) But this probably wont fix all my issues. It should always be plugged for timing checks/adjustments. And no - a malfunctioning vac can will not really do much of anything besides give you a slight hiccup when transitioning from idle to main. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 28, 2008 Author Share Posted February 28, 2008 Wow! Thanks soo much GD. I have to figure out what to do about my weber.... As far as the dizzy goes, I have 4wd and a nippon-denso dizzy. Don't ask me, just how I got it. Is there a visual difference between the two? I mean could this one im going to look at be correct? Any idea what its doing running the nippon-denso dizzy, cap and rotor? Thanks again Jess Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted February 29, 2008 Author Share Posted February 29, 2008 What are the differences of the hitachi and nippon denso? What would I look for to determine what one originally came in the car? Just wondering, as I am going to meet the guy w/ the dizzy in a few hours and don't want to buy it if it isn't even supposed to be in the car. Thanks Jess EDIT I never got a reply and have no clue how to tell what ORIGIONALLY came in my car, I pushed it back to picking up the dizzy on sunday. All I have is pictures of the new dizzy and dont know how to tell the difference, plus its aftermarket and doesnt say either brand name. Is the nippon denso right or did the p.o swap everything out? I dont konw. Well are all brats 4wd? I know mine is and ive heard that only hitachi came in 4wd. Could this be some of my issue? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 1, 2008 Share Posted March 1, 2008 All Brat's were 4WD (in the US). All 4WD's had Hitachi distributors. Ergo - Your Brat came with a Hitachi distributor. They are interchangable, but it is advisable to use the corresponding coil. The ND coils drive the plugs at a higher voltage and the ND distributor is setup for this. Using an ND distributor with a Hitachi coil risks failure of the solid state ignitor inside the disty. ND coils generally have a blue top. Hitachi's are black. That's not 100% identification though. Aftermarket direct replacement's may not look the same. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 1, 2008 Author Share Posted March 1, 2008 All Brat's were 4WD (in the US). All 4WD's had Hitachi distributors. Ergo - Your Brat came with a Hitachi distributor. They are interchangable, but it is advisable to use the corresponding coil. The ND coils drive the plugs at a higher voltage and the ND distributor is setup for this. Using an ND distributor with a Hitachi coil risks failure of the solid state ignitor inside the disty. ND coils generally have a blue top. Hitachi's are black. That's not 100% identification though. Aftermarket direct replacement's may not look the same. GD Thanks a lot GD! Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 3, 2008 Author Share Posted March 3, 2008 Ok guys, swapped out my weber for another and it fixed it. Im just going to run the other weber. Could have been jet size, choke, or some other issue. Now I just have a real bad vibration to deal w/. Got new eng and trans mount installed, tire pressures up and front axles arent too bad. Doesnt really feel like a doj vibration. maybe. All I know is I have to get this 4 speed trans out and a 5 speed in quickly! Thanks guys, thanks GD! Jess Quote Link to comment Share on other sites More sharing options...
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